We will examine the effects of dark-/light-adaptation on the cephalopod visual system. We have previously noted changes in rhabkom morphology and in the distribution of photopigments in dark- vs. Light-adapted retinas. Studies outlined in this application will investigate the role of an actin-based and tubulin-based cytoskeleton in these light-/dark-induced changes. As a corollary to these studies, we are also interested in the development of the octopus photoreceptor and in correlating cytoskeletal changes with maturation of the rhabdomere. Lastly, we have noted the unequal distribution of a specific retinal protein in the dorsal vs. Ventral halves of the adult octopus retina and that this protein redistributes during dark-/-light- adaptation. We will study this protein to determine if it is involved in the light/dark changes noted above. Our methods to study rhabdom morphology, photopigment distribution and development will rely on the immunocytochemical localization of specific cytoskeletal and retinal proteins using laser scanning confocal and electron microscopy. We will use standard biochemical techniques, including subcellular fractionation, electrophoresis and amino-terminal sequencing to assist in identification of the dorsal-ventral protein. We will also prepare an antibody to the dorsal-ventral protein and localize the protein in light- /dark-adapted retinas. We will collaborate with Dr. Brian Matsumoto on cytoskeletal studies and confocal microscopy, and with Dr. Peter McCaffery and Dr. Glenn Nagel on biochemical techniques and amino-terminal sequence comparisons. Our results will provide information about the effects of light and dark on the organization of the photoreceptor cytoskeleton and on the distribution and function of an asymmetrically distributed retinal protein. Undergraduate and graduate students will be co-investigators and will work closely with the PI. Students will use sophisticated techniques to investigate timely subjects that will contribute to our knowledge of photoreceptor cell function. Students will develop a solid foundation in biomedical research to support them in continuing graduate studies.